The present invention relates to a probing method and a probing apparatus, and more specifically, to a probing method and a probing apparatus with high reliability, in which a load applied to a main chuck carrying an object of inspection thereon by probes is measured when the main chuck is overdriven to the probes, so that a steady load can always be applied to the main chuck in accordance with the measured value.
As shown in FIG. 8, a probing apparatus 10 for checking integrated circuits on a wafer for electrical properties, for example, is provided with a loading chamber 11, probing chamber 12, controller 13, and display unit 14. In the loading chamber 11, wafers W stored in a cassette C are delivered one after another and transported to the probing chamber 12. The probing chamber 12 adjoins the loading chamber 11. Integrated circuits formed on each wafer W that is transported from the loading chamber 11 are inspected in the probing chamber 12. The controller 13 controls the chambers 11 and 12. The display unit 14 doubles as a control panel for operating the controller 13.
The loading chamber 11 is provided with a pair of tweezers 15 for use as a transportation mechanism for the wafers W. The tweezers 15 move back and forth in the horizontal direction and rotates forward and reversal, thereby delivering the wafers W in the cassette C one after another and transporting them into the probing chamber 12. A sub-chuck 16 for pre-aligning each wafer W is provided near the tweezers 15. As the sub-chuck 16 receives each wafer W from the tweezers 15 and rotates forward or reversal in a θ-direction, it pre-aligns the wafer W on the basis of its orientation flat.
The probing chamber 12 is provided with a main chuck 17 that carries each wafer W thereon. The main chuck 17 is moved in X- and Y-directions by means of X- and Y-stages 18, 19, respectively, and moved in Z- and θ-directions by means of built-in drive mechanisms. Alignment means 20 is provided in the probing chamber 12. The alignment means 20 serves to align each wafer W with the probes. The alignment means 20 includes an alignment bridge 22 having first image-pickup means (e.g., a CCD camera) 21 for imaging the wafer W, a pair of guide rails 23 for guiding the bridge 22 in reciprocation in the Y-direction, and second image-pickup means (e.g., a CCD camera, not shown) attached to the main chuck 17. A probe card is provided on the top surface of the probing chamber 12. On the upper surface of the probe card, a test hed is connected electrically to the card by means of a connecting ring. A test signal from a tester 34 (see FIG. 1) is transmitted to the probe card via the test head and the connecting ring, and further transmitted from the probe card to the wafer W. The object of inspection is checked for electrical properties in accordance with the test signal.
In inspecting the integrated circuits formed on each wafer W, the tweezers 15 takes out one of the wafers W from the cassette C. While the wafer W is being transported to the probing chamber 12, it is pre-aligned on the sub-chuck 16. Thereafter, the tweezers 15 deliver the wafer W to the main chuck 17 in the probing chamber 12. The alignment bridge 22 moves to the center of the probe card. The main chuck 17 moves to the position under the first image-pickup means 21 of the bridge 22, and the wafer on the chuck 17 is aligned with the probe card by means of the first image-pickup means 21 and the second image-pickup means. As the main chuck 17 moves in the X- and Y-directions, the wafer W is subjected to index feed. As the chuck 17 ascends in the Z-direction, the electrodes of the integrated circuits are brought into contact with probes. When the main chuck 17 is overdriven, the integrated circuits on the wafer W are checked for electrical properties with their electrodes electrically in contact with the probes.
In the case of a wafer W with a diameter of 200 mm or less, as shown in FIG. 9A, the wafer W on the main chuck 17 ascends from the position indicated by a dashed line to the position indicated by a full line as the main chuck 17 is overdriven. As indicated by a full line in FIG. 9A, the wafer W rises in the Z-direction without substantially tilting from its horizontal position. As this is done, each probe 24A of a probe card 24 is elastically raised from the position of the dashed line to the position of the full line of FIG. 9A. The tip of the probe 24A moves from a starting point S to an ending point E, as indicated by a thick line. The plane distance covered by the tip that moves from the starting point S to the ending point E, as indicated by a hatched arrow in FIG. 9B, is within the area of an electrode pad P of each integrated circuit. Thus, the probes 24A and the electrode pad P are brought electrically into contact with each other, whereupon the integrated circuit is inspected.
In the case of a wafer W with a diameter of 300 mm, the wafer size is too large, and besides, the integrated circuits are hyperfine, and electrode pads are arranged at narrow pitches. The number of pins of the probe card is increased (e.g., to 2,000) correspondingly. A load from about 2,000 probes 24A that acts on the main chuck 17 when the chuck is overdriven is as heavy as, for example, more than 10 kg to 20 kg. Accordingly, an unbalanced load that is generated when the wafer W is overdriven from the position indicated by a dashed line in FIG. 10A so that it touches the probes 24A causes the rotating shaft (not shown) of the main chuck 17 to bend. In consequence, the wafer W is tilted for about 20 to 30 μm, for example, as indicated by a full line in FIG. 10A, and deflected outward from its original raised position. As this is done, the tip of each probe 24A is elastically raised from the position indicated by the dashed line to the position indicated by the full line of FIG. 10A, and moves along a track (indicated by a thick line in FIG. 10A) that is longer than the one shown in FIG. 9A. Although the starting point S of the tip is situated in the same position as the one shown in FIG. 9A, the ending point E is located outside the area of the electrode pad P, as indicated by a hatched arrow in FIG. 10B. Thus, test signals cannot be transmitted from the probes 24A to the electrode pads P, so that the reliability of the inspection is lowered.
In Jpn. Pat. Appln. KOKAI Publication No. 11-30651, the inventor hereof proposed a probing method and a probing apparatus in which dislocation of probes attributable to contact load is corrected three-dimensionally. According to this technique, the probes estimate a distortion of a main chuck in the position where the probes are in contact with a wafer, in accordance with known data, such as information (outside diameter, material, etc.) on the main chuck, information (outside diameter, number of chips, etc.) on the wafer, and information (probe tip area, number of probes, etc.) on a probe card. Based on the estimated value, the position where the probes are in contact with the wafer is corrected three-dimensionally.